Always create indexes

Have you ever thought what it would be like to look up a phone number in
the phone book of a major metropolitan city if the book were not indexed by
name? For example, to look up the phone number for John Jones, you could not
go straight to the J page. You would have to read
the entire book. That is what a table scan is like. Derby has to read
the entire table to retrieve what you are looking for unless you create useful
indexes on your table.